Mercenaries Supplemental II is the second expansion to Field Manual: Mercenaries Revised. It includes information on lesser-known hiring halls and unit briefs for less-famous mercenary commands, including some that are rogue and/or wanted. The rules section contains information for non-standard mercenaries and alternate eras of play. These include new life paths for CBT: RPG characters and new experience paths for creating a mercenary unit, as well as information on Noisiel, the new hiring hall. Also included in this book are tables for alternate eras, including random 'Mech assignment tables and a listing of when certain military technologies were developed and when they were put into production by which faction.

A companion volume to Classic BattleTech Field Manual: Mercenaries, Revised, and Mercenaries Supplemental, Mercenaries Supplemental II delves into the dregs of the mercenary world, allowing players to use these unique mercenaries in their Classic BattleTech campaigns. Additional rules for mercenary creation include non-BattleMech Unit Tech Levels, special renegade and freelancer mercenary paths, as well as rules for playing mercenaries in different BattleTech eras, from the Star League, to the Succession Wars, to the present.